Self-propelled washing device using reduced internal pressure for adhering to a vertical or inclined surface

ABSTRACT

A self-propelled washing apparatus comprises a housing having an interior which opens toward an open side of the housing; a flexible member air-tightly coupled to the open side of the housing; a drive mechanism for engaging a vertical or inclined support surface along which the apparatus is to be propelled to wash the support surface; and a device for producing reduced pressure in the interior of the housing. When the open side of the housing is placed against the support surface, the reduced pressure in the interior of the housing causes the housing to move toward the support surface and to flex the flexible member. Most of the reaction force to the moving of the housing comes from a contact force between the drive mechanism and the support surface. This contact force maintains positive and accurate driving of the apparatus along the support surface.

BACKGROUND OF THE INVENTION

[0001] This invention relates to self-propelled washing devices, and more particularly to self-propelled, self-adhering washing devices for use in washing windows on vertical or inclined surfaces of tall buildings and the like.

[0002] Various window washing devices are known. However, these known devices suffer from various disadvantages, such as being too large, complex and heavy. None of the known devices are capable of being used by a user reaching a hand through an opening in a building and placing the device on the surface of a window to be cleaned. Moreover, the known devices are heavy and could cause a dangerous situation if they fell off of a window.

[0003] The object of the present invention is to provide a simple, light-weight, easy to use, window washing device for use on vertical or steeply inclined surfaces of tall buildings and the like.

[0004] A further object of the present invention is to provide such a device which is low in cost and which is easy to manufacture.

[0005] A further object of the invention is to provide such a device which is compact and light in weight (no more than about 2 kg, and preferably less than about 0.5 kg) so that the device can be placed by hand on the window surface, being cleaned by reaching out of an opening, and so that if the device becomes disengaged from the surface being washed, substantially no danger to pedestrians will be caused if the device falls to the ground.

[0006] A further object of the invention is to provide such a device which is easy to control by a user, and which reliably adheres to the surface being washed.

SUMMARY OF THE INVENTION

[0007] According to a first aspect of the present invention, a self-propelled washing apparatus comprises a housing having a cover member and side walls, the housing having an interior defined within the cover member and side walls and opening toward an open side of the housing; a flexible member air-tightly coupled to the side walls at the open side of the housing; a drive mechanism coupled to the housing and having at least one contact surface adapted to engage a vertical or inclined support surface along which the washing apparatus is to be propelled to wash the support surface; a device for producing reduced pressure in the interior of the housing, the produced reduced pressure in the interior of the housing being less than the pressure at the exterior of the housing; and a device coupled to the housing for applying a cleaning fluid to the support surface. When the open side of the housing of the washing apparatus is placed against the support surface which is to be cleaned and along which the washing apparatus is to be propelled, the differential pressure between the reduced pressure in the interior of the housing and the pressure outside of the housing causes the housing to move toward the support surface and to flex the flexible member, whereby most of the reaction force to the moving of the housing comes from a contact force between the at least one contact surface of the drive mechanism and the support surface along which the washing apparatus is to be propelled, the contact force maintaining positive and accurate driving of the washing apparatus along the support surface.

[0008] According to another aspect of the present invention, a self-propelled washing apparatus comprises a housing having a cover member and side walls, the housing having an interior defined within the cover member and side walls and opening toward an open side of the housing; a drive mechanism coupled to the housing and having at least one contact surface adapted to engage a vertical or inclined support surface along which the washing apparatus is to be propelled to wash the support surface; a device for producing reduced pressure in the interior of the housing, the produced reduced pressure in the interior of the housing being less than the pressure at the exterior of the housing; a device coupled to the housing for applying a cleaning fluid to the support surface; and flexible means for enabling the housing to move toward the support surface when the open side of the housing is placed against the support surface responsive to the reduced pressure being produced.

[0009] When the open side of the housing of the washing apparatus is placed against the support surface which is to be cleaned and along which the washing apparatus is to be propelled, the differential pressure between the reduced pressure in the interior of the housing and the pressure outside of the housing causes the housing to move toward the support surface, whereby most of the reaction force to the moving of the housing comes from a contact force between the at least one contact surface of the drive mechanism and the support surface along which the washing apparatus is to be propelled, the contact force maintaining positive and accurate driving of the washing apparatus along the support surface.

[0010] According to yet another aspect of the invention, a method of washing windows on a substantially vertical surface of a tall building comprises providing a self-propelled washing apparatus including a housing having a cover member and side walls, the housing having an interior defined within the cover member and side walls and opening toward an open side of the housing; a drive mechanism coupled to the housing and having at least one contact surface adapted to engage a vertical or inclined outer window surface of the tall building and along which the washing apparatus is to be propelled to wash the window surface; a device for producing reduced pressure in the interior of the housing, the produced reduced pressure in the interior of the housing being less than the pressure at the exterior of the housing; and a device coupled to the housing for applying a cleaning fluid to the window surface. The washing apparatus as applied to the outer window surface by hand through an opening in the building such that the open side of the housing of the washing apparatus is against the outer window surface along which the washing apparatus is to be propelled, the differential pressure between the reduced pressure in the interior of the housing and the pressure outside of the housing causing the housing to move toward the window surface. The driving of the washing apparatus along the window surface is controlled from inside the building, wherein most of the reaction force to the moving of the housing comes from a contact force between the at least one contact surface of the drive mechanism and the window surface along which the washing apparatus is to be propelled.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]FIG. 1 is a sectional view of a self-propelled vacuum-adhering window washer according to the present invention;

[0012]FIG. 2 is a sectional view thereof taken along line II-II in FIG. 1;

[0013]FIG. 3 is a sectional view thereof, taken along line III-III in FIG. 1;

[0014]FIG. 4 is a perspective view of a typical wiper blade for use in the present invention;

[0015]FIGS. 5 and 6 show examples of flexible connection portions between the housing 7 and the sealing member 6; and

[0016]FIG. 7 shows a circuit diagram of a typical controller for the drive motors.

DETAILED DESCRIPTION

[0017] Referring to FIG. 1, the self-propelled vacuum-adhering window washer of the present invention comprises an outer housing 7, preferably made of molded rigid plastic material, and which is generally rectangular in shape. The outer housing 7 comprises a cover member 7 a and side walls 7 b, 7 c, 7 d and 7 e extending downwardly from the cover member 7 a and preferably integrally formed (by molding) with the cover member 7 a. The outer housing 7 further comprises a flexible portion 5 around the outer periphery thereof, adjacent the area where the surface 13 of a window or the like is contacted, and a lower peripheral bearing or sealing edge portion 6 extending from the flexible portions and which contacts the surface 13 of the window or the like which is being cleaned by the device of the present invention. The peripheral sealing edge portion 6 is also preferably made of a molded rigid plastic material. Springs 31 lightly bias the sealing edge portion 6 away from the main housing 7.

[0018] The flexible portion 5 around the outer periphery of the housing 7 could be located differently. For example, a flexible portion could be located on the sidewalls closer to the cover member 7 a. Still further, the flexible portion need not be as illustrated in the drawings. Any type of flexible member having sufficient resilience can be used. Moreover, the sealing edge portion 6 can be made integral with the flexible portion 5. If the flexible portion 5 has sufficient springiness, the springs 31 could be eliminated. In the system shown in the present drawings, the resilient member 5 is made, for example, of a highly resilient material, such as nylon material or fabric, such as parachute fabric, which does not have springiness. Thus, the springs 31 are required in such an embodiment.

[0019] Mounted at opposite ends of the housing 7 are wiper housings 2 (see FIG. 1) which hold respective wipers 4 via respective springs 3 spaced along the length of the wipers 4. The wipers 4 are in the form of wiper blades as shown, for example, in FIG. 4. The length of the respective wiper blades 4 is a function of the length of the sides of the main housing 7 to which the wiper housings 2 are attached. Instead of springs 3, a leaf spring or resilient rubber or elastomeric material could be used.

[0020] The wiper housings 2 have channels 20 therein through which a cleaning liquid is passed, and from which the cleaning liquid is sprayed out as spray 1 (for example, through nozzles at the outlets of channels 20). The cleaning liquid is supplied to passages 20 via hoses 17, as will be described hereinbelow. The cleaning liquid could be dispensed in liquid streams or drops instead of as a spray. Other delivery techniques, such as a wet sponge-type material or the like, could be used to deliver cleaning liquid to the surface being cleaned. While the cleaning liquid is shown being dispensed outside of the housing 7, it could be dispensed inside of the housing 7 and wipers could be provided inside of the housing 7.

[0021] The sealing edge portions 6 could serve as wipers, replacing the wiper housing 2 and wiper blades 4. With such a system where the sealing edge portions 6 serve as wipers, the cleaning liquid could be dispensed either inside or outside of the housing 7, preferably in the vicinity of the sealing edge portions 6.

[0022] The housing 7 is propelled along surface 13 by motor driven wheels 9 which preferably have O-rings made of rubber or the like around the outer periphery thereof to enhance traction against the surface 13 of the window being washed. See FIG. 3. Instead of O-rings, the wheels 9 could have outer surfaces made of high friction elastomeric material to enhance traction. The wheels 9 are driven by respective motors 11 which are preferably DC motors with gear reduction. The motors 11 are driven by an external power supply such as electric mains or batteries via electrical wires 12. The motors 11 are connected to an external controller (see FIG. 7) which supplies the external electrical power via wires 12. The driving of the device by the wheels 9 is described later hereinbelow.

[0023] The wheels 9 are supported by rigid support members 10 which are connected to or are integrally formed with the housing 7, for example as shown in FIG. 3. The support members 10 are preferably made of plastic and can be adhered to housing 7 by use of an adhesive or plastic welding (i.e., ultrasonic welding). Preferably a molded plastic structure (i.e., of PVC) is provided wherein the wheel supports 10 are integrally molded with the housing. Other members which are shown as being attached, such as the wiper housings 2 for example, can be integrally molded with the housing 7.

[0024] The system also comprises a supply tube 15 which is connected to an air compressor remote from the window washing device. Compressed air is fed from a compressor through supply tube 15 and then through tubes 19 and 20 to a Venturi area 8. The fluid (compressed air) exiting the tube 20 through Venturi area 8 creates a low pressure (vacuum) inside the main housing 7. The air from inside the main housing 7 is sucked or drawn out (shown by arrows 26 in FIG. 2) through openings 30 between the inner Venturi tube 20 and the outlet tube 22, thus creating a low pressure or vacuum (PIN) within the housing 7. The high speed air 27 is exhausted through the right hand side of outlet tube 22, as shown in FIG. 2. The exhaust air is shown by reference numeral 23. As a result, the pressure PIN (inside the housing 7) shown in FIG. 2 is less than the pressure POUT (outside the housing 7). This maintains the suction force required to keep the housing securely against the surface 13 of the window being cleaned.

[0025] A typical example is as follows:

[0026] Pressure of Compressed air→3 Atm

[0027] P_(in)≦0.9 Atm (kg/cm²⁾

[0028] Air speed at outlet≈30 to 40 meters/sec

[0029] Typical contact force between vertical surface being cleaned and the wheels of the drive mechanism: $\begin{matrix} {{c\quad o\quad n\quad t\quad {ac}\quad t\quad f\quad o\quad r\quad c\quad e} = {{L \times {W\left( {P_{o\quad u\quad t} - P_{i\quad n}} \right)}} - f}} \\ {= {{{200\quad {cm}^{3} \times 0.1} - 0.75} = {19.25\quad k\quad g}}} \end{matrix}\quad$

[0030] where:

[0031] f=biasing force of springs 31 and flexible member 5≈0.75 kg)

[0032] P_(in)=pressure inside housing 7

[0033] P_(out)=atmospheric pressure (=1)

[0034] Another equation of interest is:

Contact force×μ>total weight of apparatus

[0035] where:

[0036] μ=coefficient of friction between driving wheel and surface being cleaned

[0037] Typically μ=0.15 for wet surfaces and a typical weight is 0.5 kg

[0038] The cleaning fluid is fed into the system through a tube 17 which runs independently within the compressed air tube 15. This tube 17 is connected to the coupling 21 for the wiper housings 2 so as to produce the spray 1 as shown in FIG. 1. The connection of tube 17 (see FIGS. 1 and 2) between the hose 15 and the connection 21 is not shown in the drawings for ease of illustration. The pressure of the cleaning fluid entering through tube 17 is sufficient to produce the spray 1 at the outlet nozzles of the wiper housings 2.

[0039] In the illustrated embodiment, the housing 7 is propelled along surface 13 by the two wheels 9 (see FIG. 3) which have the rubber O-rings 24 around the outer periphery thereof to better grip the surface 13 on which the device is propelled.

[0040] As described above, the main housing 7 has a lower peripheral sealing portion 6 which is connected to the main housing by a peripheral flexible member 5. The flexible member 5 is a highly resilient member adhered to the lower edge of housing 7 and the upper edge of sealing member 6. The sealing member 5 is air tight, and is preferably made of an air pervious nylon material or fabric, such as parachute fabric. The sealing member 6 is biased away from the housing member 7 by means of springs 31 which are spaced around the sides of the housing 7. Two springs 31 are shown along the rear wall of housing 7, but the other side walls of housing 7 each preferably have two identical spring members for evenly biasing the sealing member 6 away from the housing member 7. In use, when compressed air is supplied through supply tube 15 so as to create the low pressure or vacuum within the housing 7, the housing 7 is caused to move toward the surface 13 of the window or the like along which the device is propelled, against the very light biasing force f of springs 31. As shown above, a typical biasing force f is about 0.75 kg. This downward force (about 19.25 kg in the above example) which presses the wheels 9 against the surface 13 provides secure traction force for the wheels 9 against the surface 13, thereby enabling accurate and positive propelling of the device along the surface 13. If the sealing member 6 hits an obstruction or the like, even slight lifting off of the sealing member 6 from the surface 13 at one portion thereof does not cause disengagement of the device, since the low pressure or vacuum within the device 7 is sufficient to maintain the light-weight device (no more than about 2 kg, and preferably less than about 0.5 kg) against the surface 13, even with a slightly reduced differential pressure. Moreover, even the slightly reduced differential pressure, which is still sufficient to maintain attraction of the device to the surface 13, the wheels 9 have sufficient driving force to positively and accurately propel the device along surface 13.

[0041] As mentioned above, the wheels 9 are driven by respective motors 11 through wires 12 which also pass through the compressed air supply tube (see FIG. 2) to outside of the device. The wires 12 are connected to a control circuit (FIG. 7) and provide controlled power to the motors 11 so as to provide the desired degree of control of movement of the washing device.

[0042] Referring to FIG. 7, showing a typical controller, to move the device forward, both wheels are driven in the forward direction by moving switch 71 to the “forward” position to appropriate electrical power (i.e., two 9 volt batteries) to the motors 11 via wires 12. To make a turn, one wheel 9 is stopped or slowed down relative to the other wheel (by operating switch 72 to the “right” or “left” position), thereby changing the direction of movement of the device. Of course, to stop movement, the electrical power to both motors 11 is turned off (center position of switch 71), and to reverse movement, the polarity of the power to motors 11 is reversed (“reverse” position of switch 71).

[0043] A tether such as a strong wire or elongated nylon member, can also be passed through supply tube 15 and be anchored at the housing 7 and at the end thereof remote from the washing device to prevent the washing device from falling if, by chance, it becomes disengaged from the surface 13 of the window or the like which is being washed. Such a tether can be independently connected to the housing 7 (without passing through tube 15) to serve the same purpose as described above.

[0044] Since the device of the present invention is relatively light (no more than about 2 kg, or preferably less than about 0.5 kg), even if it falls to the ground, the chances of it hurting someone are minimized, especially with the preferred weight of less than 0.5 kg.

[0045] By reducing the pressure inside the housing 7, a sufficient suction force is provided for maintaining the washing device in positive contact with the surface 13 of the window or the like being washed, and also sufficient reduced pressure is provided inside the housing 7 to create a reaction force for pressing the gripping surfaces of the driving wheels against the surface 13, so as to provide positive and secure driving forces so as to enable movement of the device to be easily and accurately and reliably controlled.

[0046] Instead of wheels 9, tractor or caterpillar-like drives could be used. Such tractor or caterpillar-type drives would have outer surfaces with a high coefficient of friction, such as rubber, elastomeric material or the like, so that accurate and reliable driving of the washing device along the surface being cleaned can be achieved, even if the surface being cleaned is wet or damp. The wheels shown in the drawings are shown only by way of example, and are not limiting of the drive mechanism.

[0047] As shown in FIG. 3, each wheel support 10 is connected to the housing 7 and comprises two legs, between which the respective wheels 9 are mounted via a respective wheel shaft 25. Instead of providing a resilient member 5 around the periphery of the side walls 7 a, 7 b, 7 c and 7 d of the housing 7, the wheels 9 could be biased away from the cover member 7 a, for example by mounting the wheels 9 on movable shafts 25, which shafts would be spring loaded in a direction away from the cover member 7 a. This would cause the wheels 9 to project outwardly from the lower edge 6 of the housing 7. The biasing force of the springs which bias the wheels 9 outwardly of the housing 7 should be very light so that only a small amount of force is required to enable the wheels 9 to move towards cover member 7 a so that the edge 6 will contact the surface 13 to be cleaned when suction pressure is applied. When using spring biased wheels instead of the flexible member 5, the user must place the washing apparatus by hand on the surface to be cleaned and press slightly down so as to cause the wheels to move inwardly of the housing and to enable the edges 6 to bear on the surface 13 being cleaned. In all other respects, operation is the same as described hereinabove.

[0048] A connector housing 16 is provided for serving as the interface between the supply tube 15 and the respective outlet tubes 17 and 19. The wires 12 are received within the connector housing 16 and are passed therethrough in a liquid and air-tight manner. Similarly, the cleaning fluid tube 17 passes through a wall of the connector housing 16 in a liquid and air-tight manner. The compressed air is fed through tube 15, into the central portion of the connector housing 16, and out through an air connector portion 18 to which the tube 19 is connected. Preferably, the tube 19 is a flexible air connector tube which supplies the compressed air from connector housing 16 to air injector inlet tube 20. The air injector inlet tube 20 is supported by support member 21, which is supported by the housing 7. The support member 21 can be adhered or otherwise connected to the housing 7.

[0049]FIG. 5 shows the construction of the flexible member 5 in greater detail. The reference numerals used in FIG. 5 are the same as the reference numerals used in FIGS. 1-3. The springs 31 (eight springs are preferably provided—two on each side surface of housing 7) are mounted to the housing 7 and sealing member 6 by spring housings 32 which are adhered or otherwise connected to the housing 7 and sealing member 6, respectively. Other connections of the spring to the housing member 7 and sealing member 6 could be used.

[0050]FIG. 6 shows another embodiment wherein the flexible member 5 is substantially the same as the flexible member 5 in FIG. 5 and in FIGS. 1-3, but wherein the lower sealing member 6 is replaced by a sealing member 60. The sealing member 60 preferably has a U-shaped opening at the bottom thereof which extends around the entire periphery of the lower surface around the device. A foam resilient member 61, for example, is mounted in the innermost portion of the U-shaped channel 62, and an O-ring 63 is mounted at the bottom-most open end of the U-shaped channel 62. The O-ring 63 extends around the entire lower periphery of the device and serves as the sealing member for abutting against the surface 13 along which the device is moved. The O-ring 63 can be made of materials which are sufficiently slippery so as to slide easily along surface 13, while also providing a pressure seal against surface 13, and while also being sufficiently strong so as not to be damaged by sliding along surface 13. Suitable materials are, for example, a rubber-like O-ring with Teflon™ or other materials having a low coefficient of friction embedded therein.

[0051] While the invention has been described above with respect to specific apparatus and structures, various alterations and modifications can be made within the scope of the appended claims. 

1. A self-propelled washing apparatus comprising: a housing having a cover member and side walls, said housing having an interior defined within said cover member and side walls and opening toward an open side of said housing; a flexible member air-tightly coupled to said side walls at the open side of said housing; a drive mechanism coupled to said housing and having at least one contact surface adapted to engage a vertical or inclined support surface along which the washing apparatus is to be propelled to wash said support surface; a device for producing reduced pressure in the interior of said housing, said produced reduced pressure in the interior of said housing being less than the pressure at the exterior of said housing; and a device coupled to said housing for applying a cleaning fluid to said support surface; wherein when said open side of said housing of said washing apparatus is placed against said support surface which is to be cleaned and along which the washing apparatus is to be propelled, the differential pressure between said reduced pressure in the interior of said housing and the pressure outside of said housing causes said housing to move toward said support surface and to flex said flexible member, whereby most of the reaction force to said moving of said housing comes from a contact force between said at least one contact surface of said drive mechanism and said support surface along which the washing apparatus is to be propelled, said contact force maintaining positive and accurate driving of said washing apparatus along said support surface.
 2. The washing apparatus according to claim 1, further comprising a blade mounted to said housing for contacting said support surface for wiping and cleaning said support surface.
 3. The washing apparatus according to claim 1, wherein said device for applying a cleaning fluid comprises a dispensing device mounted to said housing for dispensing a cleaning fluid onto said support surface.
 4. The washing apparatus according to claim 3, wherein said dispensing device is arranged to dispense said cleaning fluid outside of said housing.
 5. The washing apparatus according to claim 1, wherein said device for producing reduced pressure in the interior of said housing includes a Venturi device which receives compressed air from an external compressed air source.
 6. The washing apparatus according to claim 5, wherein said external compressed air source is connected to said housing by an elongated hose which is connected to said Venturi device.
 7. The washing apparatus according to claim 1, wherein said at least one contact surface of said drive mechanism comprises at least two drive members, each drive member having a contact surface.
 8. The washing apparatus according to claim 7, wherein said drive mechanism further comprises an electric motor drivingly coupled to each of said at least two drive members.
 9. The washing apparatus according to claim 8, wherein said electric motors are connected to a switched power source arranged externally of said housing.
 10. The washing apparatus according to claim 1, wherein the total weight of said housing, flexible member, drive mechanism, device for producing reduced pressure and device for applying a cleaning fluid is no more than about 2 kg, and preferably no more than about 0.5 kg.
 11. The washing apparatus according to claim 1, wherein said drive mechanism is mounted in the interior of said housing.
 12. The washing apparatus according to claim 1, wherein said flexible member is arranged at a portion of said side walls adjacent said open side of said housing, and includes a surface for bearing and sealing against said support surface.
 13. The washing apparatus according to claim 1, further comprising at least one resilient spring coupled to said flexible member for biasing said flexible member in a direction toward said open side of said housing.
 14. A self-propelled washing apparatus comprising: a housing having a cover member and side walls, said housing having an interior defined within said cover member and side walls and opening toward an open side of said housing; a drive mechanism coupled to said housing and having at least one contact surface adapted to engage a vertical or inclined support surface along which the washing apparatus is to be propelled to wash said support surface; a device for producing reduced pressure in the interior of said housing, said produced reduced pressure in the interior of said housing being less than the pressure at the exterior of said housing; a device coupled to said housing for applying a cleaning fluid to said support surface; and flexible means for enabling said housing to move toward said support surface when said open side of said housing is placed against said support surface responsive to said reduced pressure being produced; wherein when said open side of said housing of said washing apparatus is placed against said support surface which is to be cleaned and along which the washing apparatus is to be propelled, the differential pressure between said reduced pressure in the interior of said housing and the pressure outside of said housing causes said housing to move toward said support surface, whereby most of the reaction force to said moving of said housing comes from a contact force between said at least one contact surface of said drive mechanism and said support surface along which the washing apparatus is to be propelled, said contact force maintaining positive and accurate driving of said washing apparatus along said support surface.
 15. The washing apparatus according to claim 14, further comprising a blade mounted to said housing for contacting said support surface for wiping and cleaning said support surface.
 16. The washing apparatus according to claim 14, wherein said device for applying a cleaning fluid comprises a dispensing device mounted to said housing for dispensing a cleaning fluid onto said support surface.
 17. The washing apparatus according to claim 16, wherein said dispensing device is arranged to dispense said cleaning fluid outside of said housing.
 18. The washing apparatus according to claim 14, wherein said device for producing reduced pressure in the interior of said housing includes a Venturi device which receives compressed air from an external compressed air source.
 19. The washing apparatus according to claim 18, wherein said external compressed air source is connected to said housing by an elongated hose which is connected to said Venturi device.
 20. The washing apparatus according to claim 14, wherein said at least one contact surface of said drive mechanism comprises at least two drive members, each drive member having a contact surface.
 21. The washing apparatus according to claim 20, wherein said drive mechanism further comprises an electric motor drivingly coupled to each of said at least two drive members.
 22. The washing apparatus according to claim 21, wherein said electric motors are connected to a switched power source arranged externally of said housing.
 23. The washing apparatus according to claim 14, wherein the total weight of said housing, flexible means, drive mechanism, device for producing reduced pressure and device for applying a cleaning fluid is no more than about 2 kg, and preferably no more than about 0.5 kg.
 24. The washing apparatus according to claim 14, wherein said drive mechanism is mounted in the interior of said housing.
 25. A method of washing windows on a substantially vertical surface of a tall building, comprising: providing a self-propelled washing apparatus including a housing having a cover member and side walls, said housing having an interior defined within said cover member and side walls and opening toward an open side of said housing; a drive mechanism coupled to said housing and having at least one contact surface adapted to engage a vertical or inclined outer window surface of the tall building and along which the washing apparatus is to be propelled to wash said window surface; a device for producing reduced pressure in the interior of said housing, said produced reduced pressure in the interior of said housing being less than the pressure at the exterior of said housing; and a device coupled to said housing for applying a cleaning fluid to said window surface; applying said washing apparatus to said outer window surface by hand through an opening in said building such that said open side of said housing of said washing apparatus is against said outer window surface along which the washing apparatus is to be propelled, the differential pressure between said reduced pressure in the interior of said housing and the pressure outside of said housing causing said housing to move toward said window surface, controlling driving of said washing apparatus along said window surface from inside said building, wherein most of the reaction force to said moving of said housing comes from a contact force between said at least one contact surface of said drive mechanism and said window surface along which the washing apparatus is to be propelled.
 26. The method according to claim 25, further comprising mounting a blade to said housing for contacting said support surface for wiping and cleaning said support surface.
 27. The method according to claim 25, comprising dispensing said cleaning fluid onto said support surface by said device for applying a cleaning fluid.
 28. The method according to claim 27, comprising dispensing said cleaning fluid outside of said housing.
 29. The method according to claim 25, comprising producing reduced pressure in the interior of said housing by a Venturi device which receives compressed air from an external compressed air source.
 30. The method according to claim 29, comprising connecting said external compressed air source to said housing by an elongated hose which is connected to said Venturi device.
 31. The method according to claim 25, comprising providing said at least one contact surface of said drive mechanism as at least two drive members, each drive member having a contact surface.
 32. The method according to claim 31, comprising providing said drive mechanism with an electric motor drivingly coupled to each of said at least two drive members.
 33. The method according to claim 32, comprising coupling said electric motors to a switched power source arranged externally of said housing.
 34. The method according to claim 25, wherein the total weight of said housing, drive mechanism, device for producing reduced pressure and device for applying a cleaning fluid is no more than about 2 kg, and preferably no more than about 0.5 kg. 